It is known to provide a continuously variable transmission in which the rotation of an output shaft is dependent upon the difference between the speeds of rotation of an input shaft and an alternate shaft. Andrus, U.S. Pat. No. 2,745,297 discloses a reversible speed changer with a drive shaft and a counter shaft. The drive shaft is connected to a sun gear and the counter shaft is connected to a ring gear. A planetary gear system is connected between the ring gear and the sun gear. An output shaft is operatively connected to the planetary gears such that rotation of the planetary gears will result in rotation of the output shaft. The speed of rotation of the output shaft is dependent upon the difference between the linear speeds of rotation of the sun gear and the ring gear. This difference in speeds of rotation can be controlled by a variable power take-off which variably couples the counter shaft to the input shaft. The transmission disclosed by Andrus produces relatively show speeds and relatively low torque.
Gillade, U.S. Pat. No. 4,406,178, discloses a power transmission in which an input shaft is connected to a sun gear. The input shaft is coupled to a driven shaft which is variably coupled to a disk on which planetary gears are mounted. The planetary gears mesh with the sun gear and with an output gear which is connected to an output shaft. Rotation of the output shaft is dependent upon the difference in linear speeds of rotation of the disk and the sun gear.